1. Field of the Invention
This invention relates generally to satellite constellations and more particularly to constellations providing continuous global or regional coverage.
2. Description of Related Art
As a new era in space based intelligence gathering is being entered, threats to national security are no longer geographically constrained and intelligence gathering on a ubiquitous, global scale has become a necessity. As a result, a variety of space-based radar applications are being developed.
Constellations of satellites having earth coverage capabilities are well known and have been well documented. Generally, such systems fall into two broad categories, namely, constellations having polar orbits and those having non-polar or inclined orbits. Most current and planned satellite constellations in space having a requirement to provide continuous global coverage are based on uniform planar spacing using Walker orbital designations, wherein Walker constellations consisting of a plurality of equally spaced circular orbits having particular orbital inclinations are fully identified by: (1) a three integer code reference T/P/F, where T is the total number of satellites in the pattern, P is the number of planes between which the number of satellites are equally divided, and F is a measure of the relative phasing of satellites in adjacent planes; and (2) the inclination angle, i, of all the orbital planes relative to a reference plane which is typically the equator of the earth.
A review of constellation design, including Walker constellations, has been set forth in a publication entitled xe2x80x9cMission Design and Implementation Of Satellite Constellationsxe2x80x9d, published by Kluwer Academic Publishers in the Proceedings of an International Workshop, held in Toulouse, France, 1997, and edited by Jozef C. van der Ha, pp. 373-393.
It is an object of the present invention, therefore, to provide a reduction in the number of satellites required to provide continuous global or regional coverage.
It is a further object of the invention to provide a constellation of satellites including a plurality of inclined orbits.
It is yet another object of the invention to provide continuous global or regional coverage by satellites including a plurality of inclined orbits having non-uniform or asymmetrical spacing and fewer in number than Walker constellations.
These and other objects are achieved by a non-uniform planar spaced constellation of satellites for providing continuous world-wide or regional coverage for applications including, but not limited to, space based radar and, comprising: at least one pair of orbital planes including a plurality of satellites having inclined co-rotating orbits; at least one other orbital plane immediately adjacent one orbital plane of said at least one pair of orbital planes and including a plurality of satellites having an inclined counter-rotating orbit; and wherein the fields of view of the satellites in said at least one pair of co-rotating orbital planes form an overlapped array of hexagonal packing at the equator and the field of view of the satellites in said one co-rotating orbital plane and said one other counter-rotating orbital plane form an overlapped array of rectangular packing at the equator, and wherein the spacing between said at least one pair of co-rotating orbital planes is greater than the spacing between said at least one other counter-rotating orbital plane and said one co-rotating orbital plane.
Further scope of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood, however, that the detailed description and specific embodiment, while disclosing the preferred embodiment of the invention, it should be noted that it is being provided by way of illustration only, since various changes and modifications coming within the spirit and scope of the invention will become apparent to those skilled in the art from the following detailed description.